Circuit breakers
View Sequence overviewStudents will:
- plan and conduct an experiment into the factors that affect the flow of electricity in a circuit.
- understand that electrical energy is ‘shared’ in a circuit.
- understand that electrical energy can be transformed into light energy, heat energy, or sound energy.
In this lesson, students will represent their understanding in these ways:
- describe factors that affect the brightness of a bulb.
- describe why a house might need more electrical energy at night.
- participate in and contribute to discussions, sharing information, experiences and opinions.
- update the TWLH chart.
In this lesson, assessment is formative.
Feedback might focus on:
- Are students able to describe how they used variables in the experiment?
- Are students able to use the model of electric circuits to provide explanations for their results?
- Are students reasoning and justification based on evidence they have collected?
Whole class
Class science journal (digital or hard-copy)
Stripping pliers (to strip the insulation from the wires if required)
Demonstration copy of Light it up investigation planner Resource sheet
Materials to create a word wall
Each group
3 x 1.5V AA battery
3 x 1.5V battery holder
3 x light bulb holder
3 x 1.5V light bulb (+ spares)
6 x 10 cm length of insulated wire, with the ends stripped of insulation (+ spares)
High Tech option: a light meter to test the amount of light (lux) provided by a bulb
Note: If no electrical equipment is available, the Circuit Construction Kit on the PHET website can be used.
Safety note
The voltage marked on bulbs is the maximum recommended voltage, so exceeding it might cause the bulbs to stop working. If additional batteries are correctly added to a circuit, then the circuit’s total voltage is the sum of their individual voltages. If students wish to investigate the effect of the number of batteries, ask them to use a circuit with three bulbs in series (as the voltage of the circuit is then divided among the bulbs).
Each student
Individual science journal (digital or hard-copy)
Light it up investigation planner Resource sheet
Lesson
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkRe-orient
Remind students of the bicycle chain model and the delivery model of electricity from the previous lesson.
Ask students to imagine that a blackout interrupted the energy travelling to the school. Discuss how the bicycle chain model or the delivery model could be used to demonstrate an interruption to the energy flow.
- What happened to the wheels in the bicycle chain model when you pushed on the pedals?
- What could you do to stop the wheels from moving?
- What about the delivery model? How could you stop the cars delivering the Blu Tack to the bulb?
- What would both of these look like in real life?
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkIdentifying and constructing questions is the creative driver of the inquiry process. It allows students to explore what they know and how they know it. During the Inquire phase of the LIA Framework, the Question routine allows for past activities to be reviewed and to set the scene for the investigation that students will undertake. The use of effective questioning techniques can influence students’ view and interpretation of upcoming content, open them to exploration and link to their current interests and science capital.
When designing a teaching sequence, it is important to spend some time considering the mindset of students at the start of each Inquire phase. What do you want students to be thinking about, what do they already know and what is the best way for them to approach the task? What might tap into their curiosity?
Read more about using the LIA FrameworkSupply and demand
Pose the question: What affects the supply of electrical energy and causes a blackout?
If students haven’t asked this question themselves in the TWLH chart, add it to the list of class questions and discuss how answering this question will be the centre of today’s investigation.
Discuss and list factors that could affect the supply of electricity to the school and students' homes.
Remind students that a brownout is a reduction in electricity that means the remaining electricity needs to be redirected to key areas such as hospitals. Discuss which areas/industries that need electricity might be considered essential.
Sharing electricity in a circuit
A light bulb glows brightly when it receives enough electrical energy from its energy source.
A light bulb glows brightly when it receives enough electrical energy from its energy source. The amount of electrical energy available to each bulb can vary depending on the number or voltages of the batteries, or the number and arrangement of the bulbs.
A light bulb glows brightly when it receives enough electrical energy from its energy source. The amount of electrical energy available to each bulb can vary depending on the number or voltages of the batteries, or the number and arrangement of the bulbs.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkThe Investigate routine provides students with an opportunity to explore the key ideas of science, to plan and conduct an investigation, and to gather and record data. The investigations are designed to systematically develop content knowledge and skills through increasingly complex processes of structured inquiry, guided inquiry and open inquiry approaches. Students are encouraged to process data to identify trends and patterns and link them to the real-world context of the teaching sequence.
When designing a teaching sequence, consider the diagnostic assessment (Launch phase) that identified the alternative conceptions that students held. Are there activities that challenge these ideas and provide openings for discussion? What content knowledge and skills do students need to be able to complete the final (Act phase) task? How could you systematically build these through the investigation routines? Are there opportunities to build students’ understanding and skills in the science inquiry processes through the successive investigations?
Read more about using the LIA FrameworkMultiple bulbs
Discuss:
- how electrons transfer the electrical energy around the entire circuit.
- how the electrical energy is transformed into light energy by the bulb.
Ask students to reflect on the electrical circuits they made in Lesson 2. What factors could interrupt the supply of enough electrical energy for the bulbs to transform into light energy?
Using a variables grid in the class science journal, record possible elements of the circuit that could be changed. Variables might include the length of wire, number of wires, number of bulbs, number of batteries, and arrangement of bulbs and batteries.
Pose the investigation question: What happens to the brightness of the bulb when we change_____________? Invite teams to complete the question by selecting their own variable to test.
Each team should complete the Predict (P) and Reason (R) sections of the Predict, Reason, Observe, and Explain (PROE) strategy.
If any teams decide to add multiple bulbs to the circuit, they should also explain which of their bulbs they will use to measure changes in the light brightness.
Suggest that students make comparisons to their original circuits that contain a single light bulb.
Decide how students will measure the brightness of the bulb:
- NO TECH: If no equipment is available, the Circuit Construction Kit on the PHET website can be used. The varying brightness of the bulb is represented by the length of the lines emanating from it.
- LOW TECH: The brightness of the original circuits containing a single light bulb can be represented as: ++. A brighter lightbulb can be represented with +++ and a dimmer bulb with +.
- HIGH TECH: A light meter (or appropriate app) can be used to measure light in ‘lux’ units. This is an opportunity to discuss why using eyesight can be subjective and affected by looking at a bright object for a few minutes and then looking away.
Allow time to conduct the investigation and record results.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkFollowing an investigation, the Integrate routine provides time and space for data to be evaluated and insights to be synthesized. It reveals new insights, consolidates and refines representations, generalises context and broadens students’ perspectives. It allows student thinking to become visible and opens formative feedback opportunities. It may also lead to further questions being asked, allowing the Inquire phase to start again.
When designing a teaching sequence, consider the diagnostic assessment that was undertaken during the Launch phase. Consider if alternative conceptions could be used as a jumping off point to discussions. How could students represent their learning in a way that would support formative feedback opportunities? Could small summative assessment occur at different stages in the teaching sequence?
Read more about using the LIA FrameworkLighting the way
Invite teams to report their findings to the rest of the class, including presenting a claim that answers their specific investigation question with supporting evidence and reasoning.
- What did you predict would happen?
- What did you observe?
- Was your prediction different from what you observed?
- Why do you think that happened?
- What claim might you make to answer your question “What happens to the brightness of the bulb when we change_____________?”
- What evidence do you have to support your claim?
Compare the results of teams who changed the same variable to see if they achieved the same results, and discuss how this may or may not have happened. Encourage students to question each other using the Science Question Starters.
Compare the findings of the student teams to the models of electrical circuits from the previous lesson. Use their models to explain their findings.
- Adding more lights to a single circuit means the energy carried by the current needs to be shared. This means the individual light bulbs have less light energy.
- A light bulb in a single circuit will be brighter if there are two batteries to provide energy.
- After some time, the battery goes flat and provides no energy to the bulb.
If any team tested adding more bulbs to the circuit, did they find that this resulted in the bulbs not producing light? Discuss and link this to a potential cause for a blackout or a brownout.
- What happened when light bulbs were added to the circuit?
- Why do you think the bulbs were not able to produce light?
- There was not enough electrical energy to be transformed into light energy.
- Have you ever had the lights go out when too many things were plugged in?
- How could you make sure there was enough electrical energy for the lights in the circuit?
- We could add more batteries, or use fewer bulbs.
- Do you think this could cause a blackout (or brownout)?
- Who do you think needs electricity the most…schools…homes…shops…hospitals?
- If you controlled the electricity in a town, how would you decide who should be disconnected if there was not enough current for everyone?
Reflect on this lesson
You might:
- discuss examples of where the concepts of this lesson might apply in daily life.
- record teams' claims and evidence about circuits from their investigations in the L and H columns of the TWLH chart.
Alternative conceptions
What alternative conceptions about electrical energy might students hold?
If students have retained the ‘consumption’ model, then they might think that less ‘stuff’ returns to the battery after going through the light bulb. If they connect light bulbs in series, they might think that the second bulb will receive less ‘stuff’ than the first one, and therefore the brightest bulb will be the closest to the battery and the lights will get progressively dimmer. However, all electrons start moving at the same time across the circuit and through the light bulbs, so they split the available voltage instantly.
Some students might think that using longer or shorter lengths of wire will affect the brightness. If the wire is very long it might be harder for the electricity to flow through. However, generally modifying the length slightly does not make any appreciable difference to the brightness of the bulb.
If students have retained the ‘consumption’ model, then they might think that less ‘stuff’ returns to the battery after going through the light bulb. If they connect light bulbs in series, they might think that the second bulb will receive less ‘stuff’ than the first one, and therefore the brightest bulb will be the closest to the battery and the lights will get progressively dimmer. However, all electrons start moving at the same time across the circuit and through the light bulbs, so they split the available voltage instantly.
Some students might think that using longer or shorter lengths of wire will affect the brightness. If the wire is very long it might be harder for the electricity to flow through. However, generally modifying the length slightly does not make any appreciable difference to the brightness of the bulb.
Brownout
A brownout is a sudden drop in the electrical voltage in the grid.
A brownout is a sudden drop in the electrical voltage in the grid. This can be due to reducing the load in an emergency, or by a sudden increase in demand. Students may experience this if they use a generator in their home, or on a hot/cold day when people return home and switch on their heaters/air-conditioners.
A brownout is a sudden drop in the electrical voltage in the grid. This can be due to reducing the load in an emergency, or by a sudden increase in demand. Students may experience this if they use a generator in their home, or on a hot/cold day when people return home and switch on their heaters/air-conditioners.